TcPO2: Measures PO2
•Before Pulse Oximetry was available, TCOM was used as a surrogate for arterial PO2 in neonates. 
•Still being used in a variety of ways to monitor patients with sleep apnea, post operatively, and neonates.
–Pulse oximetry and transcutaneous oxygen tension for detection of hypoxemia in critically ill infants and children.
J Pediatr. 1985 Sep;107(3):362-6.
Fanconi S, Doherty P, Edmonds JF, Barker GA, Bohn DJ.
–Home monitoring of transcutaneous oxygen tension in the early detection of hypoxaemia in infants and young children  CF Poets, MP Samuels, JP Noyes, KA Jones and DP Southall
Department of Paediatrics, National Heart and Lung Institute, Royal Brompton Hospital, London. Archives of Disease in Childhood, Vol 66, 676-682, Copyright © 1991 by Archives of Disease in Childhood.
–Transcutaneous Pco2 monitoring in critically ill adults: Clinical evaluation of a new sensor *. Critical Care Medicine. 33(10):2203-2206, October 2005.
Bendjelid, Karim MD, MS; Schutz, Nicolas MD; Stotz, Martin MD; Gerard, Isabelle MD; Suter, Peter M. MD, FCCM, FCCP; Romand, Jacques-Andre MD, FCCM
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We evaluated a new pulse oximeter designed to monitor beat-to-beat arterial oxygen saturation (SaO2) and compared the monitored SaO2 with arterial samples measured by co-oximetry. In 40 critically ill children (112 data sets) with a mean age of 3.9 years (range 1 day to 19 years), SaO2 ranged from 57% to 100%, and PaO2 from 27 to 128 mm Hg, heart rates from 85 to 210 beats per minute, hematocrit from 20% to 67%, and fetal hemoglobin levels from 1.3% to 60%; peripheral temperatures varied between 26.5 degrees and 36.5 degrees C. Linear correlation analysis revealed a good agreement between simultaneous pulse oximeter values and both directly measured SaO2 (r = 0.95) and that calculated from measured arterial PaO2 (r = 0.95). The device detected several otherwise unrecognized drops in SaO2 but failed to function in four patients with poor peripheral perfusion secondary to low cardiac output. Simultaneous measurements with a tcPO2 electrode showed a similarly good correlation with PaO22 (r = 0.91), but the differences between the two measurements were much wider (mean 7.1 +/- 10.3 mm Hg, range -14 to +49 mm Hg) than the differences between pulse oximeter SaO2 and measured SaO2 (1.5% +/- 3.5%, range -7.5% to -9%) and were not predictable. We conclude that pulse oximetry is a reliable and accurate noninvasive device for measuring saturation, which because of its rapid response time may be an important advance in monitoring changes in oxygenation and guiding oxygen therapy.
Home monitoring of transcutaneous oxygen tension in the early detection of hypoxaemia in infants and young children
CF Poets, MP Samuels, JP Noyes, KA Jones and DP Southall
Department of Paediatrics, National Heart and Lung Institute, Royal Brompton Hospital, London.
Twenty three patients (age range 0.5-40 months) with recurrent cyanotic episodes underwent physiological recordings, including transcutaneous oxygen tension (TcPO2) from a monitor modified for use at home (Kontron 821S). Of 69 episodes in which the arterial oxygen saturation (SaO2, Nellcor N200) was less than or equal to 80% for greater than or equal to 20 seconds and/or central cyanosis was present, the TcPO2 monitor alarmed (less than or equal to 20 mmHg or 2.67 kPa) in every episode. The pulse oximeter identified hypoxaemia in 62 out of 69 episodes, failing in seven episodes due to signal loss from movement artefact. In only seven of 69 episodes was there an accompanying apnoeic pause (greater than or equal to 20 seconds), and heart rate fell to less than or equal to 80 beats/minute in only five of 28 episodes in which an electrocardiogram was recorded. In 32 episodes in which SaO2 fell to less than or equal to 60%, the TcPO2 monitor alarmed after a median time interval of 16 seconds (maximum time interval 30 seconds). The TcPO2 monitor was then used in an uncontrolled trial at home in 350 patients at increased risk of sudden death and/or hypoxaemia. Indications for monitoring included apparent life threatening events or cyanotic episodes (n = 163), prematurity and prematurity related disorders (n = 86), and sudden unexpected death in one or more siblings (n = 122). The TcPO2 monitor detected cyanotic episodes at home in 81 patients, 52 of whom received vigorous stimulation and/or mouth to mouth resuscitation. Twenty one of these 52 patients had further hypoxaemic episodes documented in hospital with pulse oximetry.(ABSTRACT TRUNCATED AT 250 WORDS)